The lateral check ligament of the eye is one of two check ligaments (the other being the medial check ligament), which limit the movement of the lateral and medial rectus. The motor units of these extrinsic eye muscles contain the smallest number of muscle fibers (5-10) of any muscle in the body. Because of this, the eyes move together so that they are aligned when looking at something. A person whose eyes are not coordinated well enough to produce this alignment is said to have strabismus, or squint.